Field
The present disclosure generally relates to methods and apparatus for processing a substrate, and more specifically to methods and apparatus for reducing photoresist microbridge defects.
Description of the Related Art
Integrated circuits have evolved into complex devices that can include millions of components (e.g., transistors, capacitors, and resistors) on a single microchip. Photolithography is a process which may be utilized to pattern or shape various material layers during fabrication of the chip. Generally, the process of photolithography involves depositing a photoresist layer on a substrate, masking the substrate, and exposing the photoresist layer to electromagnetic radiation. The photoresist layer may be a chemically amplified photoresist and may include a resist resin and a photoacid generator. The photoacid generator, upon exposure to electromagnetic radiation, generates acid which alters the solubility of the photoresist in a development process. Excess solvent utilized in the development process and solvated resist may then be removed to reveal a patterned material layer suitable for subsequent fabrication processes.
During exposure of the photoresist, a photomask or reticle may be used to selectively expose certain regions of the photoresist layer to form a desired pattern on the substrate. However, the photomask or reticle utilized to pattern the photoresist may be defective and result in a patterned photoresist which is undesirable. A defect in patterning of the photoresist may result in the undesirable pattern being transferred to other layers on the substrate during subsequent processing operations. For example, as illustrated in FIG. 1 (prior art), a substrate 100 includes a material layer 102, a patterned resist layer 104, and exposed regions 106. A microbridge defect 108, which may result from defects during photolithography, undesirably bridges the exposed area 106 where no resist material should exist after exposure. Microbridge defects may result from mask defects or from defects in the photoresist, such as compositional heterogeneity with regard to photo acid generator concentration in specific regions of the photoresist. Microbridge defects are increasingly troublesome as critical device dimensions are continually shrinking. Additionally, microbridge defects reduce production yields and contribute to increased processing costs and reduced efficiencies.
Thus, there is a need for improved methods and an apparatus for reducing patterning defects in microelectronic devices.